

#include <string.h>
#include "base64.h"

#if 0
static const char  *codes =   
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";  
#endif 
  
static const unsigned char  map[256] = {  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 253, 255,  
255, 253, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 253, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255,  62, 255, 255, 255,  63,  
 52,  53,  54,  55,  56,  57,  58,  59,  60,  61, 255, 255,  
255, 254, 255, 255, 255,   0,   1,   2,   3,   4,   5,   6,  
  7,   8,   9,  10,  11,  12,  13,  14,  15,  16,  17,  18,  
 19,  20,  21,  22,  23,  24,  25, 255, 255, 255, 255, 255,  
255,  26,  27,  28,  29,  30,  31,  32,  33,  34,  35,  36,  
 37,  38,  39,  40,  41,  42,  43,  44,  45,  46,  47,  48,  
 49,  50,  51, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,  
255, 255, 255, 255 };

short base64_decode(const unsigned char *in, unsigned char *out, unsigned short len)
{  
    unsigned long t;
	unsigned short x;
	unsigned long y;
	unsigned short z;  
    unsigned char c;  
    int g = 3;  
  
    for (x = y = z = t = 0; x < len;) {  
        c = map[in[x++]];
        if (c == 255) return -1;  
        if (c == 253) continue;  
        if (c == 254) { c = 0; g--; }  
        t = (t<<6)|c;  
        if (++y == 4) {  
            out[z++] = (unsigned char)((t>>16)&255);  
            if (g > 1) out[z++] = (unsigned char)((t>>8)&255);  
            if (g > 2) out[z++] = (unsigned char)(t&255);  
            y = t = 0;  
        }  
    } 
    return z;  
}